The invention concerns a scanner, especially one for the detection of one- and/or two-dimensional codes with a receiving optics that projects the image of a reading line onto a linear array of several photoreceivers, and an illumination arrangement for linearly illuminating the entire reading line.
Such scanners are known, are called line scanners, and can identify unidimensional codes located in the reading line without requiring relative movement between the scanner and the code.
However, if the code moves past the scanner in a transport direction, the scanner can also detect two-dimensional codes as a result of such relative movement.
Scanners operating in this manner often have the drawback that codes are defectively and incompletely identified, or in a worst case not at all, due to inadequate lighting conditions or light intensity along the reading line.
Even when it is feasible to compensate for a low illumination intensity with longer light exposures, a reduced reading speed results. Especially on conveyor lines, a major field of application for such scanners, reduced conveying speeds result, which is a significant disadvantage. In order to lessen this limitation, the codes were illuminated with high-energy light sources, such as sodium vapor lamps, laser diodes, or many diffusely radiating LEDs. This in turn results in a large and expensive scanner with a high electrical power consumption that leads to a significant heating of the scanner.
The term “light” as used in this application is not restricted to visible light. Thus, the word “light” is meant to encompass electromagnetic radiation in general, i.e. UV light, IR light, as well as visible light, which can normally be used for the operation of such scanners.